Found one of Wentworth's early interviews.

Miller: Well, they're all new to me, so... [Laughs] I am constantly being surprised. Everyone is so great, and everyone's got a fully fleshed-out, multidimensional character. I'm particularly intrigued by Sara Lance's journey. She's clearly badass, but she's also got a code. You can see her moral struggle, and that's a model for Snart, because he's got his own code. He's got his own struggle. So I think he's focused on her for a variety of reasons. Source